Figure: Master students at ACES performing experiments on Sea Spray formation during a laboration which I've developed.

Before I came to ACES, I was student counsellor at Department of Meteorology (MISU), where I also taught in meteorology and chemical meteorology.

From 2001-2005, I was the coordinator for the NordForsk Network for Atmospheric Aerosol Dynamics. We arranged 2 international Ph.D. courses per year, with 15–25 students in each course. I was like an international graduate school headmaster. After that, I served for several years in the board of the NordForsk graduate school C-BACCI.

Education and supervision of students matter for me, and I care deeply about the quality of the education. Both theoretical understanding of details, a good overview of the complex system of climate and biosphere-atmosphere-ocean-geosphere-litosphere interactions are important to transfer to the students, as well as concrete skills that matter for the subject.

Supervision of Master students and Ph.D. students are also an important part of my work. In my view, this is the part of education where I have the largest responsibility towards the student. I'm now on my 12th Ph.D. student (see list below).

Aministration

At ACES I have over the years have various administrative duties. Currently, I'm a member of the ES-ABC-Master program council, I am also ACES Environmental contact person. As such I lead ACES Environmental group, I am responsible to derive a new Environmental plan each year, and to suggest it to the department prefect and board, and to carry out various activities in the plan, and in the long run to achieve our goal of Climate neutrality in 2040.

-The primary marine aerosol source (sea spray): sea salt, organic compounds, biological and toxic particles. We use both direct flux measurements over the oceans, and laboraoty experiments. We evaluate our data in terms of source parameterisations, where the sea spray emissions are functions of key parameters such as wind, water temperature, salinity, sea ice etc., to enable these processes to be represented in models.

-Primary urban traffic aerosol emissions: combustion particles as well as mechanically produced particles from the road, tires or breaks. We analyse the data in term of vehicle type, traffic activity, speed, etc. or if the road is dry or wet. We present the result in term of Emission Factors, which makes it possible to represent these sources in models. We were also able to show that the large aerosol emissions from road vehicles in spring in Stockholm is because when the road dry up in spring, mechanically generated particles that has been captures by ice and water during the winter, are released.

We are currently working on a new data set where a ELPI+ (Dekati inc.) was used for the Eddy Covariance aerosol fluxes, which gave us the number flux from 14 channels from 7nm to 10 μm Diameter (D). See below. Thereby, we cover both the lower size range where particles originate from vehicle fossil fuel combustion, and the larger range where they originate from brakes, tyres and road surface. Previous measurements using OPCs mainly detected the mechanical generated particles.

-Ship Emissions, which are an important source of aerosols. I have good data from the Baltic Sea from 2011 to the present. We intend to examine how the emissions changed in 2015 when the fuel sulfate level decreased, compare emissions for different types of ships, different age, speed etc. Finally we will deliver so called emission factors that can be used to represent this aerosol source in air quality and climate models.

-Representation of these processes in air-quality models and climate models and what effect they have on climate change.

In the past, I’ve also worked on:

-Secondary aerosol sources: nucleation of new particles and subsequent growth, in interaction with dynamic atmospheric processes, e.g. turbulence, and the horisontal scale of nucleation and growth in entire (or large part of) air masses.

-Emissions of primary biogenic aerosol particles from the Amazonian rain forests and oceans.

-Aerosol dry deposition fluxes over different surfaces, measured and modelled.

-Arctic sulfur and sea spray aerosols, and everything that happens in the complex Arctic boundary layer over an ice covered ocean, including radiation blance and heat flux balance over sea ice, formation of Arctic fogs, low level jets etc.

Twoof our largest long term goals are being fullfilled right now through technical innovation: A) EC-fluxes from about 10nm to 10μm D with size resolution, in order to be able to follow how different source processes creates particles of different sizes. B) Chemically specified aerosol mass fluxes through the REA-flux method. It has taken about 10 years to realise these. The following 10 years we will apply these methids on didderent aerosol sources under different conditions. 

One goal remains, which has more to do with where we measure than, how and what we measure. Having studied one of the two big natural aerosol sources (sea spray) with eddy covariance flux measurements, I’d like to do the same with large emissions of dust aerosols over deserts and semi arid land. There is a risk that these emissions will increase if climate change increase wind speed and decrease soil moisture. Surprisingly, there exist only one peer review publication where people applied the EC-flux method to quantify dust aerosol emissions! 

However, so far I have not been able to take home the necessary grants to do this. But I haven’t given up…

The methods we use:

-In situ micro-meteorological measurements of aerosol fluxes, specifically emission fluxes using the eddy covariance (EC) method in e.g. the urban and marine environment, see photo of flux-tower above. I pionered this work with the first ever direct measuerments of sea spray aerosol emissions form ocean to atmosphere published in Nilsson et al. (2001). Over the years we have proceeded from using only Condensation Particles Counters (CPC) to Optical Particle Counters (OPC), and the Elecronical Low Pressure Impactor (ELPI+) to measure the flux of aerosols of different diameter, and using thermodenuders to get the flux of aerosols of different volatility. We have also improved the various flux corrections needed for the EC method. We develop our own software for both data collection and processing.

In more recent time, we have done some very promission method development: 1) We have learned to use the ELPI+ from Dekati with the EC method to measure the size resolved flux over a much wider size range (0.006 to 10 micrometer D) with less errors than for OPCs and CPCs. 2) We have built a system based on the Relaxed Eddy Accumulation (REA) method, which allow us to sample aerosols on filter for subsequent chemical analysis, followed by calculations of aerosol mass flux of specific chemical compounds.

-Laboratory experiments of aerosol production from bubble bursting in real and artificial seawater. In these experiments we controle the water temperature and salinity, and we determine the bubble number and sizes, and the sea spray aerosol number and size. Additional measurements have occasonally been added. I dare say that we have become among the word leading in this. The plan is to add a high speed camera to these experiments to be able to catch and study the bubble and sea-spray formation processes that takes place in a few milliseconds.

-Process models: for example numerical box models of aerosol dynamics, trajectory models, Monte-Carlo simulations.

-Global climate models: previously the Oslo-CAMl, and the Nor-ESM, both so called General Circulation Models or Global Climate Models (GCM) in collaboration with colleagues in Oslo, Norway.

-Analysis of in situ (network) measurements: aerosol number size distributions and supporting meteorological and chemical data from several measurements stations through international networks, campaigns and co-workers.

Parameterization for large models, emission factors etc.

There are of course many aspects of our research results, but one I’d like to promote more than others are the most refined end-results, the source or process parameterizations. The intention is to provide a reasonable way to include complex processes in large models, where these of course have to be simplified, and where this has to be done as a fair compromise between accuracy and computational efficiency. Not all our parameterization live up to this, but we are trying.

Finally, we want these parameterizations to be used by modellers. That is necessary for our research to be useful for policymakers etc. After all, climate models are the primary tool to assess future climate and how it depends on different political and economical choices. The first time someone used our sea spray source parameterization from Mårtensson et al. (2003) and published it was in 2004…and we celebrated! Over time, Mårtensson et al. (2003) became an accepted standard for sea spray source parameterization, and the only one that far that took into account the surface water temperature. Now we have replaced it with the improved parameterization of Salter et al. (2015).  With time we were also able to apply our parameterization in models ourselves, as in Mårtensson et al. (2010), Kirkevåg et al. (2013), Struthers et al. (2011, 2013) and Salter et al. (2015).

Contribution to IPCC

When IPCC in their 5th Assessment Report (2013) with a few lines cited our work in Struthers et al. (2011), on the feedback and aerosol radiative forcing caused by changes in sea spray aerosols following on changes in sea ice and water temperature due to climate change in the Arctic, it felt like a great victory after a decade of work, from experiment to GCM! In 2021, IPCC cited two more of our studies in their 6th Assessment Report (2021): One of these wasStruthers et al. (2013)

I have occationally descriped the work as an experimentalist that attempts to formulate new and improved parameterisations for climate models, air quality models etc. as being one of many who contributes with one or a few bricks in the big lego-building project representing large scale models. Collectively, these parameterisations are important for the quality of the model predictions, even if each contributions are just a few lines of code in large models, especially if they are part of so called climate-feedback processes.

Instrumentations, Resources and Software

It takes time to build up the instrument park you wish, and patience, often combining grants from more than one project. This is the key experimental resource we have:

1. A long-term aerosol flux-tower at the ICOS station at Östergarnsholm, Baltic Sea with a Gill HS ultrasonic anemometer, Licor 7500, Grimm 1.109 Optical Particle Counter (OPC)  (0.25 μm < D < 2.5 μm) , TSI 3772 Condensational Particle Counter (CPC), to which we now also add an Electrical Low Pressure Impactor (ELPI+) from Dekati Inc. The installation also include solar panels and wind turbines to drive the instruments through the year.
2. Two addiaional Eddy Covariance (EC) flux systems based on Gill ultrasonic anemometers for shorter projects at different locations, with 1 aditional Licor 7500, Grimm 1.109 OPCs and TSI CPCs.
3. Licor-610 Dew point Generator for calibration of the Licor 7500s.
4. A custom built Relaxed Eddy Accumulation System (REA) for aerosol filter sampling able to result in chemically specified aerosol mass fluxes.
5. A temperature controled (-1°C to +35°C) 50 litre stainless steel Sea Spray Simulation Tank. The tank is equiped with water sensors for salinity, temperature and Dissolved Oxygen, digital registration of the surface bubbles, a custom built Differential Mobility Sizer (DMPS)  (0.01 μm < D < 0.7 μm) and a WELAS 2300 white-light aerosol spectrometer (Palas Inc.)  (0.2 μm < D < 10 μm).
6. In the house developed software to log EC flux raw data and to control the REA flux system (SCOL), and to calculate EC fluxes (CALCEDDY) coded in Labview. In addition, code to correct aerosol EC fluxes for various errors, coded in matlab (AERES).

For many more complex projects, such as the sea spray tank simulations in the photo above, we have to colaborate with colleagues that have additional instrumentation that is of interrest for our studies, ex. H-TDMA's for aerosol hygroscopicity, Condensational Nuclei counters etc.

Where?

Since 2004 I am based in the Atmospheric Science Unit at the Department of Environmental Science (ACES) at Stockholm University. This is a great place to be in, where a lot of interesting research is performed; work that inspire us and complement our work. Most of my projects run with one or several of the other researchers here as partners, and did so already before moving here, which was one of the reasons to move. There is no sharp boarder between the research lead by different scientists here and different project link closely into each other, which helps form a creative environment. In 2004 ACES also transformed from an “Institute” into a “Department”. What was the difference? We went from a pure research institute and got the right as Department to examine students in our subject (enviornmental science). This resulted in that built up our own master programs in environmental science. It is a great opportunity to be able to influence the creation of a new education. Through ACES we also belong to several international networks/ centre of excellence and the Bolin Centre for Climate research.

Before ACES I spent my Ph.D. studies and young scientist years at the department of Meteorology at Stockholm university (MISU). In 1998-99 I spent a post-doc period at the Department of Physics of Helsinki university, in the rapidly expanding group of Prof. Markku Kulmala. Also after the period in Finland, Markku (the most cited scientist in Earth Sciences!) remained an important mentor. 

Vision

I’m enrolled in this work for two main reasons. First of all, I can’t think of anything more fun and rewarding to do (except being parent) than to plan, lead and conduct scientific research. It is like being a detective when we are trying to lure the Nature to give up her secrets, while building a better and better picture of how the Nature works. To try to understand those things I see around me like clouds or waves and how they are connected is a challenge, and much more fun (I think) than to study something more abstract. There is no lack of theoretically difficult aspects of our work (for one thing – we move around and within one of the big unsolved mysteries of science: turbulence), but on days when I’m up to my throat in administration, I can always go into the lab and grab a screwdriver or sit down and work with some data that originates from our measurements in the real atmosphere or ocean. Secondly, I find much of my motivation in the urgent need to understand the complexity of the planet Earth for reasons of the rapidly ongoing climate and environmental changes, and rapid extinction of species. It is obviously too late to stop, but we (as individuals and as society) can make choices that limit the further damages, and we have no choice but to try to adapt to those changes that are now inescapable. To do that, we need to understand what is happening and to make the best possible guesses on the future.
All my work is only a few pieces of that puzzle, but no one is going to solve the whole problem alone, it can only be done with contributions from many, many research teams around the world. Somewhere on the road (it is unclear to me when) I decided to try to make a contribution to this puzzle. Running my own research projects, building up a team that work together, participating in international projects, collaborating with many other scientists, founding my own science, supervising students-about-to-become-researchers are all part of this work and an attempt to make a larger contribution than I could myself if I worked alone.
Supervising PhD-students are perhaps the most challenging part. Imaging that you are to teach someone something you don’t know yourself! To lead someone beyond what can be found in text books or specialist magazines, to enter areas where only Nature can be the teacher. To do this one have to transfer not only knowledge, but also how to find or build new knowledge. The direct translation of “supervisor” to Swedish have a negative sound to it. The word we use in Swedish is “handledare”, which indicates that we are more of a guide, someone who “lead you by the hand”. That is more close to my vision of what sort of supervisor I wish to be, but I am beginning to realize that there is not one correct way to supervise. For each new student I have to be a new supervisor.

Sponsors:

Over the years, I have received in total ~65 million SEK (44 million SEK as main applicant) or ~5.9 million Euro, including 17 VR, 6 FORMAS, 1 VINNOVA, 2 SIDA projects, 1 Carlsbergfondet, 2 Wenner-Gren Centre and 2 Trygger grants, 1 BBCC grant, 2 NorFA grants, 2 NOS-N grant, 4 EU/EC grants.

PROJECTS:

European Union (EU), European Comission:

• 2005-09: ID 18332 - Marine Aerosol Production from natural sources (MAP) / EC FP6, co-applicant, 1.156 Mkr (of totally 23.92 Mkr)
• 2001-05: EVK2-2001-00127 - Quantification of Aerosol Nucleation in the European Boundary Layer (QUEST) / EU FP5, co-applicant, 2.765 Mkr (of totally 21.15 Mkr)
• 2002-04: EVK2-2001-00057 - Particles in the upper troposphere and lower stratosphere and their role in the climate system (PARTS) / EC FP5, main applicant 1.772 Mkr (of totally 13.135 Mkr)

Science Council (Vetenskapsrådet, VR):

• 2024-27: 2023-03814 - Sea-spray Emissions - Absent Key-processes and Evidences for Responses to Changing Climate (SEAKER-CC), main applicant, 3.84 Mkr
• 2019-22: 2018-04255 - Characterising properties of Climate Relevant Organic and Inorganic Sea-Spray-aerosols, Sources and Air-seaexchange causing their Net-emission (CROISSANT), main applicant, 3.38 Mkr
• 2015-18: 2014-05354 - Climate Effects of Sea Spray Aerosols (CESSA), main applicant, 3.4 Mkr
• 2012-16: 2011-06322 - Marine Micrometeorological and Air-Sea exchange field stations, co-applicant to Anna Rutgersson, 6.168 Mkr
• 2011-13: 2010-03821 - Marine Microbiology Influence on Sea-Spray, Clouds and Climate Forcing (MASC), main applicant, 2.6 Mkr
• 2008-11: 2007-8362 - The Green House Arctic Ocean and Climate Effects of Aerosols (GRACE), main applicant, 6.9 Mkr
• 2007-08: 2006-5050 - Primary Aerosol Emissions – Important Sources of Climate Active Aerosols, main applicant, 1.175 Mkr
• 2003-08: 622-2003-1120 - Physical Climatology, Research position / VR Rådsforskartjänst, appointed, 4.9998 Mkr
• 1999-2003: G-AA/AS 11858-302 - Climate effects of aerosol particles, Junior scientist / VR Forskarassistenttjänst, main applicant, 2.105401 Mkr

Forskningsrådet för miljö, areella näringar och samhällsbyggande (FORMAS):

• 2025-2030: 2024-02453 - Ship Exhaust Emissions under the new Low-Level-Sulfur Fuel Legislation in the European SECA-zone, Baltic Sea (SELFIE), main applicant: 5.858327 Mkr
• 2017-21: 2016-01219 - Break particles and Road dust Emission factors based on in-situ Aerosol Direct micrometeorological fluxes (BREAD), main applicant, : 3 Mkr
• 2011-13: 2010-00910 - Detecting Aerosols over the Region of Stockholm (DARS), co-applicant to Paul Glantz, 3.9 Mkr
• 2009-10: 2008-01113 - Aerobiology, a factor in environmental change, co-applicant to Åke Hagström, 1.1862 mkr
• 2008-10: 2007-01362 - Seasonal variation in the Primary Marine Aerosol Source from physical and biological/chemical processes, main applicant, 2.682 Mkr

Carl Trygger Foundation (Carl Tryggers stiftelse för vetenskaplig forskning):

• 2024-26: CTS-23:2956. Worn-out Power Grid Threatens a Unique Data Set from Östergarnsholm, Baltic Sea. Help Us Extend The Only Marine Multi-Year Aerosol Flux Measurements, Crucial to Study Sea Spray-Aerosols and Climate Change Feed-back, Main applicant, 134310 kr
• 2020-23: CTS-19:256. Measurements of particulate mass over the Baltic Sea from sea spray and ship emissions, Main applicant, 277500 kr

Who?

List of present and former students and post-docs:

M.Sc. students/Internships I have supervised:

–Monica Mårtensson (2000), later took her Ph.D. for me.
–Anna Grönlund (2001), now at SMHI.
–Stefan van Ekeren (2002-2003), then took a Ph.D. degree at Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Switzerland, now Dozent at the Saxion University of Applied Sciences, Netherlands.
–Eva Brokhöj (2003), now at SMHI (I see her name now and then when the Swedish weather service issues a storm warning!).
-Xuan Liu (2009-2010).
–Karin Jonsson (2011), now operational forcast meteorologist at SMHI.
–Sarah Howald (2012-2013). Then took at M.Sc. at Bremer University and a Ph.D. at Hamburg University, Germany.
-Julian Asplund (2021), now Ph.D. student at ACES.
-Divya Bharathi Manem (2023), now research engineer at KTH, Stockholm, Sweden.
-Yang Liu (2023-24).

Ph.D. students I have supervised:

–Yang Liu, (2025-2028), working on her Ph.D. since January 2025.
-Julika Zinke, (Ph.D. 2023), post-doc at Baltic Centre, Stockholm University.
-Andrew Butcher (Ph.D. 2013, Copenhagen University), now at Everllence, Denmark.
–Julia Zabori (Ph.D. 2012, Stockholm University), now Hydrolog at SMHI, Sweden.
–Matthias Vogt (Ph.D. 2011, Stockholm University). After a post doc in Helsinki, then worked as a researcher at NILU, Norway, focused on indoor aerosols, now researcher at Vaisala, Helsinki, Finland.
–Camilla Fahlgren (Ph.D. 2011, Linnaeus University).
–Lars Ahlm (Ph.D. 2010, Stockholm University). Made a post-doc at Scripps Institute of Oceanography, San Diego, then returned to ACES. Consult at ÅF, Stockholm, Sverige, then VINNOVA, Future Mobility, and now climate strategist at Region Stockholm.
–Kim Hultin (Ph.D. 2010, Stockholm University). Initially wind power consultant at Pöyry, Sweden, then analyst at Region Stockholm.
–Monica Mårtensson (Ph.D. 2007, Stockholm University), later worked for me as post-doc. Now at Uppsala univesity. Now at Geocenter, Uppsala university.
–Johanna Lauros (Fil. lic. 2005, Stockholm University; Ph.D. 2011, Helsinki University), now at University of Jyväskylä, Finland.
–Admir Targino (Ph.D. 2005, Stockholm University), after a post doc at University of Manchester, Centre for Atmospheric Science, U.K., now at Universidade Tecnológica Federal do Paraná, Brasil.
–Peter Tunved (Ph.D. 2004, Stockholm University), now researcher at ACES.

Post docs, Assistant Professors/Junior Researchers ACES whom worked for/with me:

–Piotr Markuszewski, my post doc starting 2020-09-01, 2 years+1 year extension, working on sea spray emissions. Back at Physcal Oceanography, Inst. of Oceanology, Polish Academy of Science. Still connected to us as an adjungated, frequently visiting scientist.
–David Hadden, my post doc starting 2019-03-18, 2 years, working on the BREAD-project, now consult at Tyrens, Stockholm, but still finnishing papers on road traffic aerosol emissions.
–Matthew Salter, my post doc 2012-2017, now at Stockholm University Baltic Sea Centre.
–Hamish Struthers, my post doc 2010-2013, now at the National Supercomputer Centre, Linköping, Sweden.
–Monica Mårtensson, my post-doc 2007-2010, now Assistant Professor at Uppsala University, Department of Geoscience, Sweden.
–Paul Glantz, came to us with an Assistant Professor/Young researcher-position from FORMAS, now Associate Professor at ACES.
–Farahnaz Khosrawi, came to us for a M. Currie-post-doc 2004-2005, now at Forschungszentrum Jülich, Germany.
–Gintautaus Buzorius, my post-doc 2002-2003, then at Center for Interdisciplinary Remotely Piloted Aircraft Studies, Naval Postgraduate School, Monterey, California, USA. Now at Upwork, San Fransisco, USA, now at Achieve, Arizona, USA.

Colaboration includes senior researchers and co-supervisors at ACES and numerous colleagues outside ACES, see specific projects.

Join us, Contact us!

If you find our research interesting, please don’t hesitate to contact us. Perhaps you are in need for a subject for your Master thesis, interested in graduate studies, or a place to spend your post doc? We are always in need for bright people. Maybe you just want a pdf of one of our papers, or help with implementing our parameterisations in your code (we typically have ready code in both matlab and Fortran). Give me a call!

Open position?

I will soon have an one open possitions as post doc in a FORMAS project on ship emissions. I just must get time for the administrative steps to announce it. Take a look at our web pages, there might also be possitions announced by my colleagues.

If you are in search of a project and supervisor for a master thesis/ex-job, me and my colleagues. have some ideas regarding projects that could suit for an exam in atmospheric science, earth sciences, environmental science, aerosol physics, meteorology, oceanography, or a civil engineering exam. Contact me if you are interested.